Imatges de pÓgina

in such a state of perfection." Captain Flinders, at page 63, vol. i. of his Voyage to Terra Australis, has the following remarks on the same appearance:

Captain Vancouver mentions having found, upon the top of Bald Head, branches of coral protruding through the sand, exactly like those seen in the coral beds beneath the surface of the sea,- -a circumstance which should seem to bespeak this country to have emerged from the ocean at no very distant period of time. This curious fact I was desirous to verify, and his description was proved to be correct. I found also two broken columns of stone, three or four feet high, formed like stumps of trees, and of a thickness superior to the body of a man; but whether they were of coral, or of wood now petrified, or whether they might not have been calcareous rocks, worn into that particular form by the weather, I cannot determine. Their elevation

above the present level of the sea could not have been less than 400 feet."

Perron says, "On breaking the branches where the incrustation is recent, we observe the woody texture contained in a solid case, and without any remarkable alteration; but, in proportion as the calcareous envelope increases, the wood becomes disorganized, and changes insensibly into a dry and black powder." From this state he supposes the centre gradually to increase in solidity till the whole mass becomes a mere sandstone, and nothing but an arborescent form indicates the ancient state of vegetation.

The incrustations near Simon's Town are of a similar nature to those found in New Holland, because, says Dr Abel, the descriptions of authors cor

respond with the appearances I have witnessed, and because I have compared a specimen brought from Bald Head in New Holland, by Mr Brown, with those I obtained at the Cape, and can trace no essential difference, either in the external characters or chemical composition. It follows from this statement, that Flinders and Vancouver have confounded vegetable incrustations with true corals; and hence the reasoning on their supposed submarine origin, and modern rising of the Bald Head, &c. above the level of the ocean, is incorrect.

Geology of the North and South, and East and West Ranges of Mountains.-The ranges of mountains which run northward from the Cape Peninsula to Orange or Gariep River, in the points where examined, exhibited granite and slate, with vast deposites of sandstone or quartz rock with numerous table-shaped summits,-thus showing a similarity of composition in these mountains to those of the Cape Peninsula.

The three great ranges of mountains that run from east to west, according to the reports of travellers, are of the same general nature, and eminently characterized by the vast abundance of sandstone reposing in horizontal strata upon the granite and slate, forming the middle, and very often the higher parts of the chains.

Geology of the Table-Land.-From the third range onwards to lat. 30° S., the prevailing rock in the plains and hills is sandstone. At Dwaal River, the frontier of the colony, there are rocks of augite-greenstone and basalt, probably in veins traversing the sandstone. Rocks of the same description, disposed in beautiful globular concre

tions, (not boulders, as stated by Burchell,) occur near to Kaabes Kraal, 29° S. lat., probably in veins traversing the horizontal sandstone of that district. The Karreebergen, or Dry Mountains, beyond the limits of the colony, form a range from five to ten miles broad, and range through the country to an unknown distance, from N. E. to S. W. These mountains are principally composed of sandstone, in horizontal strata, and everywhere exhibit beautiful table-shaped summits. According to Burchell, "The sandstone rock continues onward to lat. 30° S., to near Modde or Mud-Gap, where true quartz strata and vesicular trap-rocks make their appearance. In lat. 29° 15' 32" S., mountains, called the Asbestos Mountains, of clay-slate, disposed in horizontal strata, occur; there layers of asbestos occur in the slate. This asbestos is blue and yellow, and the fibres sometimes nearly three inches in length." In the same mountain, according to Burchell, green opal and pitchstone also occur. A range of black craggy mountains extends from the Kloof, in the Asbestos Mountains; the rocks are very probably trap. Further to the north, at Klaarwater, are vast beds of horizontally-stratified limestone, without organic remains.

Account of the Sibilo of the Africans.—At Sensavan, or Blenk-Klip, nearly in S. lat. 28°, there is a ridge of quartz rock impregnated with micaceous iron ore, which, in many places, is collected into nests of considerable magnitude. This ore of iron is known throughout Southern Africa by the name Sibilo. Hither all the surrounding nations repair for a supply of that ornamental, and, in their eyes, valuable substance. It forms, in some degree; an

article of barter with more distant tribes, and even among themselves; so that the use of it extends over at least 5° of latitude. It is of a reddish colour, soft and greasy to the feel,—its particles adhering to the skin, and staining it of a deep red colour. The skin, says Burchell, is not easily freed from these glossy particles, even by repeated washing. The mode of preparing and using it is, simply grinding it with grease, and smearing it generally over the body, but chiefly on the head; and the hair is often so much clotted and loaded with an accumulation of it, that the clots look like lumps of the ore.

From the north of Sensavan to Lattakoo, the rocks are limestone without petrifactions, granite, and slate. In conclusion, it may be remarked that, as far as is known at present, the whole of the tableland of Southern Africa, to the north of the Orange or Gariep River, is composed of horizontal limestone without petrifactions, clay-slate, sandstone or quartz rock, granite, greenstone, serpentine, and pot-stone. The most remarkable geological feature of the country is the horizontality of the strata,— thus intimating their undisturbed state.

Geological Survey of the Karroo Ground recommended. To geological travellers we recommend a particular examination of the compact clay-ground called Karroo, which, if a deposite from ancient lakes, may prove to be a tertiary formation. The surface only of the Karroo ground has been described; for, as far as our information goes, no accounts have been published of its internal structure and arrange


It is by the study of the structure and arrangement of its layers, and the careful examina

tion of the minerals, rocks, organic remains (if any) it contains, and its chemical composition, that we can acquire a distinct conception of its true na



The rivers of Africa, as far as connected with those regions of this continent described in the present volume, have been already particularly considered. As much, however, still remains to be known in regard to them, we may add, that the attention of travellers, in investigating their natural history, should, besides their geographical distribution, be directed towards the various circumstances connected with their fall, velocity, quantity of water they contain, their eddies, freshes, and bore, if any such occur; also the nature of their beds, inundations, occultations, temperature at the surface, or at different depths; their cascades and rapids; their water, as to colour, transparency, and chemical composition; and they should not omit descriptions of the riverscenery considered by itself, and also in reference to the surrounding country; and, lastly, the climate and effects of the climate, and of the scenery of the rivers, on man, ought also to form objects of inquiry.


In Southern Africa, lakes are but seldom met with, and among these, some few are salt. The most considerable salt lake hitherto met with by travellers, is that near to Algoa Bay. It is resorted to by the inhabitants from very distant parts of the colony, for the purpose of procuring salt for their own consump

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